Scintigraphic investigations of pancreatic diseases have in the past primarily utilised radiolabelled amino acids, such as C-11-L-tryptophan which has been used in positron emission tomographic (PET) studies or amino acid analogues such as selenium-75 labelled selenomethionine which has been used for planar gamma camera imaging. The use of Se-75 selenomethionine has been largely discontinued due to the high patient radiation dose associated with selenium-75 and the inconsistency of pancreatic visualisation, due in part to the relatively small quantities of this material which could be administered.
U.S. Pat. No. 4,360,511 to Baldwin et al. disclosed radioiodinated monoamine compounds which locate primarily in the brain and are useful as brain imaging agents.
Although these compounds were described as accumulating in some degree in pancreas, no data were provided on localisation of these compounds in pancreas and other abdominal organs so that it was not possible to predict their suitability for pancreatic imaging.
Kung and co-workers developed certain radioiodinated diamines, including N,N,N'-trimethyl-N'[2-hydroxy-3-methyl-5-iodobenzyl]-1,3-propanediamine (HIPDM), as indicators of brain blood flow and as brain imaging agents (Kung et al., 1983, J. Nucl. Med., Vol. 24, p. 66; U.S. Pat. No. 4,430,319 to Blau et al.)
Yamamoto's group has found some localisation of HIPDM in the pancreas of rats and mice but human clinical studies with this compound have proved disappointing in that differentiation between pancreatic and liver retention of the compound was difficult and pancreas/liver ratios are not optimal for clinical use. (Yamamoto et al., (1985), J. Nucl. Med., Vol. 26, p. 764; (1986), J. Nucl. Med., Vol. 27, p. 1013; (1990) J. Nucl. Med., Vol. 31, p. 1015).
There remains a need for convenient and discriminating pancreatic imaging agents suitable for routine diagnostic use.